FIG. 1 is block diagram of a computer system 100 in accordance with the prior art. Computer system 100 includes three main units: a host system 102, a system disk 104 and peripheral devices 110A to 110N: (where A-N represents a range of peripheral devices 110 of an arbitrary number). The computer system may be an A Series system developed by Unisys Corporation of Blue Bell, Pa., USA. or it may be any system capable of interfacing with peripheral devices 110.
The host system 102 includes a central processing unit (CPU) 112, memory 114 and an input/output processor (IOP) 116, which are all apparent to those skilled in the art. All communication between the host system 102, the system disk 104 and other devices occurs via the I/O processor 116.
The system disk 104 is connected to the host system 102 via bus 121. The system disk 104 includes an operating system 106. The operating system 106 includes an internal software driver(s) 122 which permits the host system 102 to: (1) identify external peripheral devices 110; (2) issue commands to peripheral devices 110; (3) process exceptions returned by those peripheral devices 110; and (4) command the transfer of data to and from the peripheral devices 110. A log file 118 is also included for storing, for example, system error messages and accessing violation messages. This is useful for diagnostic purposes.
The peripheral devices 110 are connected to the host system via bus 120/121. The peripheral devices 110 may employ Small Computer System Interface (SCSI) as a protocol for communication with the host system 102. Other interface protocols such as Intelligent Peripheral Interface (IPI) and Message Level Interface (MLI) can also be employed by the peripheral devices 110. Peripherals devices 110 may be either disk devices in the mega-to-giga byte range or tape devices, but may also be other devices such as CD-ROM devices.
When a new peripheral device, such as a SCSI disk device, is desired for use with computer system 100, the operating system software (along with other software) often requires modification to include information pertaining to the new peripheral device. Such modifications are desirable so that the operating system can recognize and communicate with the new disk. Such modifications, however, may force customers to upgrade to a new software release level each and every time they wish to make use of a new peripheral device which was not available at the time they obtained their current version of the operating system software. Also, internal testing and development by original equipment manufacturers (OEMs) may be hampered by the need to create a modified internal version of operating system software each time a new peripheral device may need to be investigated and/or tested.